Driving force for fluid flow
Driving force for fluid flow Driving force for fluid flow is Energy per unit mass or total head available at the point of location.
Justification:
If you observe the flow in venturi meter, it will become more clear. consider 3 points as shown in the below figure.
Assume P1, P2, P3 are pressures at 1, 2 and 3 points. Here according to cross section area variation we can say P1 > P2 < P3. It shows that P3 > P2 but fluid is moving from 2 point to 3 point, so we can sa y pressure is not the driving force. Similarly we can say velocity is also not the driving force. Why distillation? Why not adsorbption or leaching ?
In distillation the new phase generated is different from the original by phase, or heat content only. This heat can be removed or added by easy operations. But in case of adsorption or leaching the a foreign substance is introduced to separate the phases. Thenew phase generated using these processes is a new solution which in turn may be separated using other separation methods unless the new solution is directly useful. This makes thedistillation process to more economical. e conomical. Distillation process depends on the relative volatilities of the components. If the difference is too low separation is difficult and it makes the process as more expensive.
When reflux ratio to the column is minimum and zero, what are the requirements in column When reflux ratio is minimum, column requires maximum number of trays and minimum reboiler load for a required separation. To avoid this problem of infinite trays we use optimum reflux ratio. Define Intensive and extensive properties, give examples for them Intensive and Extensive properties: Extensive property: Is defined as one which depends on quantityof matter specified in the system. Examples: Total mass, volume, Energy, enthalpy, Intensive property: It is defined as one which depends on the quantity of matter present in the sysytem.
Examples: Temperature, pressure,Molar enthalpy, molar v What is jigging and where it is used ? Jigging: Jigging is a separation method in which the particle are separated by using the density difference between them. J i g g i n g is a method of gravitational preparation of natural resources, based on s e p a r a t i o n of mineral mixture on density in
vertically oscillating water stream. Usually it is used to separate metal slag form metals. What is Differential Distillation, Simple Distillation, Rayleigh distillation,Rayleigh equation, material Balance equation Differential Distillation: Simple distillation, also known as Rayleigh distillation ordifferential distillation, is the most elementary example of batchdistillation. In this distillation system, the vapor is removed from the still during a particular time interval and is condensed in the condenser. The more volatile component is richer in the vapor than in the liquid remaining in the still. Over time, the liquid remaining in the still begins to experience a decline in the concentration of the more
volatile component, while the distillate collected in the condenser becomes progressively more enriched in the more volatile component. Schematic representation of differential distillation is as shown in in fig.1 Fig:1 Differential distillation
No reflux is returned to the still, and no stages or packing materials are provided inside the column; therefore, the various operating approaches are not applicable to this distillation system. The early analysis of this process for a binary system, proposed by Rayleigh is given below. Let F be the initial binary feed to the still (mol) and x F be the mole fraction of the more volatile component (A) in the feed. Let B be the amount of compound remaining in the still, xB be the mole fraction of component A in the still, and xD be the mole fraction of component A in the vapor phase. The differential material balancefor component A can then be written as: xD dB = d ( B x B ) = B dx B + xB dB Upon integration:
or
In this simple distillation process, it is assumed that t he vapor formed within a short period is in thermodynamic equilibrium with the liquid; hence, the vapor composition (xD) is related to the liquid composition (xB) by an equilibrium relation of the form xD = F(xB). The exact relationship for a particular mixture may be obtained from a thermodynamic analysis depending on temperature and pressure. For a system following the ideal behavior given by Raoult’s law, t he equilibrium relationship between the vapor composition y (or xD) and liquid composition X (or xB) of the more volatile component in a binary mixture can be approximated using the concept of constant relative volatility (α), which is given by:
Substitution of the above equation in Equation (2)
Although the analysis of simple distillation historically represents the theoretical start of batch distillation research, a complete separation using this process is impossible unless the relativevolatility of the mixture is infinite. Therefore, the application of simple distillation is restricted to laboratory-scale distillation, where high purities are not required, or when the mixture is easily separable. what is a first order system and what physical phenomena give rise to first order system(It's transfer function)? WHAT IS A FIRST-ORDER SYSTEM? A first-order system is one whose output, y(t), is modeled by a first order,linear differential equation
Define,
��p is known as the time constant of the process and KP is called the steady state gain or static gain or simply the gainof the process. From eqn, it is easily found that the transfer function of a firstorder process is given by;
A first-order process with a transfer function given by above eqn. is also known as: first-order lag, linear lag, exponential transfer lag.
If on the other hand, a0 = 0, then from eqn. we take
which gives a transfer function
In such case the process is called purely capacitive or pure integrator
where f(t) is the input (forcing function). If a0 # 0, then above eqation yields,
Dew Point: It is the temperature at which the partial pressure of the water vapour in the mixture is equal to the vapour pressure of water. It can also be defines as, the temperature where condensate formation will start upon constant cooling of vapour mixture . Dew point is a saturation temperature Dew point is always lower than or equal to the dry bulb temperature. Dew point is always lower than or equal to the wet-bulb temperature. At 100% saturation : Dry bulb temperature = wet bulb temperature = Dew point. What is volute in centrifugal pump, uses of volute in centrifugal pump
Centrifugal pump is as shown in the figure. In this figure observe the vanes shape and impeller direction.
Volute: It is the gap between the casing and the impeller. There are two uses with volute of the centrifugal pump. 1. In this volute kinetic energy is converted into pressure energy. As the cross section area increases, the volute reduces the velocity of the liquid and increases the pressure of the liquid. 2. One of the main purposes of a volute casing is to help balance the hydraulic pressure on the shaft of the pump. However, this occurs best at the manufacturer's recommended capacity. Running volute-style pumps at a lower capacity than the manufacturer recommends can put lateral stress on the shaft of the pump, increasing wear-and-tear on the seals and bearings, and on the shaft itself.
Centrifugal pumps are used for large discharge through smaller heads. What are differences between pipe and tube,Birmingham wire gauge,schedule number Pipes and tubes are specified in terms of their diameter and wall thickness. Pipes: Heavy walled Relatively large in diameter comes in moderate lengths (20 to 40 ft) Threading is not possible Pipe walls are rough Lengths of pipes are joined by screwed, flanged and welded fittings Made by welding , casting, or piercing a billet in a piercing mill The wall thickness of the pipe is indicated usingschedule number Size of the pipe is indicated as nominal diameter Tubes: Thin walled Less diameter available in the form of coils also, several hundred meters Can be threaded Tube walls are smooth
These are joined by compression fittings, flare fittings, or soldered fittings These can be cold drawn Tube thickness is indicated using BWG (Birminghamwire gauge) Size of the tube is indicated as outside diameter NPSH is an acronym for Net Positive Suction Head. In any cross-section of a generic hydraulic circuit, the NPSH parameter shows the difference between the actual pressure of a liquid in a pipeline and the liquid's vapor pressure at a given temperature.
NPSH is an important parameter to take into account when designing a circuit: whenever the liquid pressure drops below the vapor pressure, liquid boiling occurs, and the final effect w ill be cavitation: vapor bubbles may reduce or stop the liquid flow, as well as damage the system.
Considering the circuit shown in the picture
where h L is the head loss between 0 and 1 p 0 is the pressure at the water surface p v is the vapour pressure (saturation pressure) for the fluid at the temperature T 1 at 1 Δz is the difference in height z 1 − z 0 (shown as H on the diagram) from the water surface to the location 1 ρ is the fluid density g is gravitational acceleration
